Posts Tagged: Lygus bug
Emily Bick's AAUW Grant: Targeting the Lygus Bug
Watch out, lygus bugs! Agricultural entomologist Emily Bick is targeting you. Lygus hesperus, a...
Agricultural entomologist Emily Bick doing field work in Denmark before the lockdown due to the coronavirus pandemic precautions..
Emily Bick (right) in an engagement photo with her fiance, Nora Forbes. Bick is an agricultural entomologist and a postdoctoral fellow in the lab of Lene Sigsgaard at the University of Copenhagan and Forbes is a statistician at the Danish Medtronic office.
2016 Insecticide Efficacy Trial for Lygus Bug Control in Central Coast Strawberry
Lygus bug (Lygus hesperus) (Fig. 1) is a major pest of strawberry in the Central Coast. Lygus bug populations develop on weed hosts surrounding the strawberry fields such as wild radish, common groundsel, lupines, and mustards (Zalom et al. 2012). Time to time, adults migrate into the strawberry fields and lay eggs. Eggs hatch, and molt through five nymphal stages before molting into adults. Lygus bug feeding on the developing embryos affects the normal development of tissues surrounding the embryo (Handley and Pollard 1993) and affected fruits are misshapen often referred as “catfaced fruit” (Fig. 2) which are deemed unmarketable. Although both nymphs and adults can cause catface injury, nymphs are considered more destructive than adults. The young fruits up to ~10 days after petal fall are considered vulnerable to economic injury from lygus bug feeding (Zalom et al. 2012).
Chemical control continues to be an effective tool for lygus bug control and growers are always seeking effective and softer insecticides for its control. A replicated trial comparing the efficacy of insecticide treatments against lygus bug was conducted in first-year strawberry ‘San Andreas' in Watsonville, CA in 2016. The details on insecticide products and rates used in the trial are shown in Table 1. The insecticides were applied twice at 10 day interval using commercial tractor mounted sprayer. The water volume used for both the applications was 150 gal per acre and was applied at 140 psi. Dyne-Amic (surfactant) was added at 0.25% v/v to all the treatments. Insect samples were collected using regular sized Rubbermaid container by hitting 20 flowering strawberry plants with lid. In addition, 60 fruits were sampled from each plot to determine catface injury.
Pre-count sample did not show any difference in number of adult and nymphal lygus bugs among treatments (Figs. 3 and 4). Overall, all the insecticide treatments reduced the number of lygus bug adults and nymphs compared with untreated plants. The combination treatments using pyrethroid insecticides such as Danitol and Brigade suppressed lygus bugs and general predators such as bigeyed bug, minute pirate bug, and damsel bug as well as spiders (Figs. 5-8). Data show that reduced-risk insecticides, Rimon and Beleaf suppressed lygus bug nymphs as well. Sequoia, not yet registered on strawberry, provided a decent lygus bug control. Sivanto initially provided a good suppression of adults and nymphs but could not adequately sustain the control for more than a week. Two rates of Avaunt (unregistered insecticide on strawberry) was included in this experiment and were comparable to other effective insecticides in this experiment.
Insecticide use certainly reduced catface injury on strawberry fruit. Number of fruits with catface injury was lower in all the insecticide treated plants than untreated except the lower rate of Avaunt (Fig. 9). Catface injury on fruits treated with Sequoia was lower than untreated but not different from other insecticides (except lower rate of Avaunt).
References
Handley, D. T., and J. E. Pollard. 1993. Microscopic examination of tarnished plant bug (Heteroptera: Miridae) feeding damage to strawberry. J. Econ. Entomol. 86: 505-510.
Zalom, F. G., M. P. Bolda, S. K. Dara, and S. Joseph. 2012. Strawberry: Lygus bug. UC Pest Management Guidelines, UC ANR Publication 3468.http://www.ipm.ucdavis.edu/PMG/r734300111.html
Figure 1: Lygus bug adult.
Figure 2: Catfacing of strawberry fruit.
Table 1
Figure 3. Mean number of lygus bug adults collected by week from treated plants.
Figure 4. Mean number of lygus bug nymphs collected by week from treated plants.
Figure 5. Overall mean number of lygus bug adults collected from treated plants.
Figure 6. Overall mean number of lygus bug nymphs collected from the plants.
Figure 7. Overall mean number of predatory bugs collected from treated plants.
Figure 8. Overall mean of spiders collected from treated plants.
Figure 9. Percentage fruit with catface (lygus bug feeding) injury.
A Big Cheer for a Crab Spider
What happened in our pollinator garden on June 3 probably would have promoted a standing ovation...
A crab spider nails an agricultural pest, a lygus bug. (Photo by Kathy Keatley Garvey)
Targeting Lygus Bugs
If you've ever grown strawberries, you're probably familiar with what the lygus bug does. This...
Lygus bug (Lygus hesperus) is a major agricultural pest. (Photo by Kathy Keatley Garvey)
MPede and Aza-Direct for Control of Lygus Bugs in Blackberries
As many Central Coast caneberry growers know, this summer season has seen an astonishing number of lygus bugs in blackberries. Counts of 10 to 20 lygus bugs per shake easily rival the heaviest infestations in strawberry.
However, contrary to the “catfacing” or misshapen fruit left by lygus activity in strawberry, there does not seem to be a documented type of damage from lygus in blackberry. All the same, customers have been getting tetchy about having bugs in their baskets of fruit, so it is indeed important for us as an industry to take this on.
Unfortunately, management of lygus in blackberry has proven to be just as difficult in blackberry as strawberry, perhaps even more so since there are fewer insecticides registered for use in blackberries.
Thrips incidentally occur in blackberry flowers as well and did in great numbers in this trial. Again it is not certain whether or not they cause a lot of damage. Nevertheless, thrips were also evaluated in this trial since they are a known pest in other crops and situations.
The organically registered insecticides MPede and Aza-Direct have shown promise in controlling stink bugs (same insect order as lygus bugs), so the study described below is a screen these two materials compared against a grower applied standard of Diazinon along with an untreated control.
Trial was composed of 4 24 ft x 26 ft replicated treatments in a blackberry field with significant lygus and thrips activity. MPede and Aza-Direct were applied with a motorized backpack sprayer by Brian Deeter from Gowan Company. Diazinon was applied at the label rate by the grower in an adjacent block, so while not part of the experimental design, it did provide reasonably strong information in comparison to the three other treatments.
My research assistant and I did the evaluations which consisted of shaking 3 feet of flowering blackberry hedgerow into a five gallon bucket for the lygus and agitating three mature flowers individually onto a white sheet of paper and counting the expulsed thrips there. Dates of evaluation were August 11 (pre-application), August 15 and August 19 (one week post application).
As the reader can see from the chart below, beyond Diazinon there is little effect on field populations of lygus or thrips from either MPede or Aza-Direct. Furthermore, the lack of thorough control of lygus and thrips by Diazinon, long regarded as one of the most powerful pesticides available to blackberry growers, is unsettling.
Character Rated |
lygus |
thrips |
lygus |
thrips |
lygus |
thrips |
|||||||
Rating Date |
Pre-app |
Pre-app |
8/15/2011 |
8/15/2011 |
8/19/2011 |
8/19/2011 |
|||||||
1 |
MPede + Aza-Direct |
35.75 |
a |
84.50 |
a |
31.50 |
a |
72.00 |
ab |
16.50 |
a |
54.75 |
ab |
2 |
MPede |
28.75 |
a |
56.50 |
a |
37.25 |
a |
120.25 |
a |
19.50 |
a |
67.75 |
a |
3 |
UTC |
36.00 |
a |
73.50 |
a |
34.75 |
a |
104.75 |
a |
15.50 |
a |
52.00 |
ab |
4 |
Diazinon |
22.50 |
a |
38.25 |
a |
11.25 |
b |
34.50 |
b |
11.50 |
a |
24.25 |
b |
Means followed by same letter do not significantly differ (P=.05, Student-Newman-Keuls)
Mean comparisons performed only when AOV Treatment P(F) is significant at mean comparison OSL.
Finally, it will be worth my while to return to this field to evaluate the effect, if any, this pest load is having on fruit development. As already mentioned above, beyond the contamination of harvested fruit, thrips and lygus damage to blackberry has not yet been well defined.
There are a number of pesticides mentioned for management of lygus and thrips in this article. Before using any of these products, check with your local Agricultural Commissioner's Office and consult product labels for current status of product registration, restrictions, and use information.
Lygus bug adult on unopened blackberry flower